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Tests for Thymus Cancer
Certain signs and symptoms might suggest a thymus tumor, but tests are needed to know for sure. If your doctor thinks you might have a thymus tumor (thymoma or thymic carcinoma), they will ask you about symptoms and use one or more exams or tests to check for one.
Medical history and physical exam
If you have signs or symptoms that suggest you might have a thymus tumor, your doctor will want to take a complete medical history to learn more about your symptoms. You will also be asked about your general health.
A physical exam provides information about possible signs of thymic tumors and other health problems. People with thymic tumors will sometimes have a fullness that the doctor can feel in the lower neck area.
Thymomas are often suspected if you have signs and symptoms linked with myasthenia gravis, hypogammaglobulinemia, or pure red cell aplasia. Learn more about these conditions in Signs and Symptoms of Thymus Cancers.
Imaging tests
Imaging tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of your body. Imaging tests may be done for many reasons, including to:
- Help find a suspicious area that might be cancer
- Learn how far cancer may have spread
- Help see if treatment is working
- Look for signs that cancer has come back
A chest x-ray may be the first imaging test a doctor orders if they suspect a problem in the middle of the chest. It may be able to show if there is a tumor in the chest. Sometimes, a chest x-ray may find a tumor when a person is having the test done for another reason.
Some thymomas are small or in places that might not show up on a chest x-ray. If you have a chest x-ray and your doctor wants to see more, or if they see a change on the chest x-ray, they may order a CT scan.
A CT scan uses x-rays to make detailed, cross-sectional images of your body.
Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body. A chest CT is often done using an IV contrast. This is a special dye that is put into a person's blood before the test. It help make any tumors stand out more on the images.
CT scans can also be used to help guide a biopsy needle precisely into tissue that might be a tumor. This is called a CT-guided needle biopsy.
Like CT scans, MRI scans give detailed images of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays.
An MRI of the chest may be done to look more closely at thymus tumors. This test is most often used for people who can’t have a CT scan for medical reasons, such as problems with the IV contrast. MRI images are also very useful in looking for cancer that might have spread to the brain or spinal cord.
During a PET scan, you are injected with a slightly radioactive form of sugar. This substance collects mainly in cancer cells. A special camera is then used to create a picture of areas of radioactivity in the body. The picture is not detailed like a CT or MRI scan. But a PET scan can look for possible areas of cancer spread throughout the body at once.
A PET scan can be useful in different situations:
- It can help give the doctor a better idea of whether a change seen on another imaging test is a tumor or not.
- If you have already been diagnosed with cancer, your doctor may use this test to see if the cancer has spread to lymph nodes or other parts of the body.
Certain machines can do a PET and CT scan at the same time (PET/CT scan). This lets the doctor compare areas of higher radioactivity on the PET scan with the more detailed pictures of that area on the CT. Combined PET/CT is used more often than a PET scan alone when looking at thymomas.
Blood tests
Blood tests are not used to diagnose thymomas, but they may be helpful in some situations. For example, blood tests may be done to:
- Look for certain antibodies if myasthenia gravis (MG) or another autoimmune disorder is suspected
- Make sure a mass in the middle of the chest isn’t a germ cell tumor or part of the thyroid gland
If a thymoma is diagnosed, blood cell counts and blood chemistry tests are done to get an idea of a person’s overall health, especially if surgery is planned.
People getting chemotherapy also need regular blood tests to make sure the chemo medicines aren’t harming the bone marrow, kidneys, or other organs.
Blood tests for myasthenia gravis are done before any surgery. This is because MG is very common in people with thymomas. If it’s not treated, it can cause problems with the drugs used during surgery.
Biopsies
Although signs, symptoms, and imaging tests can suggest that a thymic tumor is likely, doctors can’t be certain of the diagnosis without looking at cells from the tumor under a microscope.
To confirm the diagnosis of most cancers, doctors remove a small piece of the tumor and look at it under a microscope. This is called a biopsy.
For thymomas, a biopsy isn’t often done because doctors can usually tell that the tumor is very likely a thymoma based on how it looks on imaging tests. Because of this, doctors often remove the entire tumor during surgery, rather than do a biopsy. This provides tissue for a diagnosis and treats the tumor at the same time. The tumor is sent to the lab after surgery to confirm the diagnosis.
If the tumor can't be removed completely during surgery, a biopsy might be done to confirm the diagnosis. This helps the doctor decide if more treatment is needed after surgery.
Doctors choose the biopsy approach that best avoids spreading tumor cells into the chest cavity. They try to avoid going through the lining of the lung (the pleura) to reach the tumor, since this could make later treatment more difficult. This is called a transpleural approach. A biopsy might be done with a long, hollow needle (a core needle biopsy) or during surgery (an open biopsy).
If the doctor suspects a different type of tumor, a biopsy (usually a needle biopsy) might be done before surgery.
See Testing Biopsy and Cytology Specimens for Cancer to learn more about types of biopsies, how the tissue is used in the lab to diagnose cancer, and what the results may show.
- Written by
- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
Carter BW, Marom EM, Detterbeck FC. Approaching the Patient with an Anterior Mediastinal Mass: A Guide for Radiologists. J Thorac Oncol. 2014;9(9 Suppl 2):S110-118.
Falkson CB, Bezjak A, Darling G, et al. The Management of Thymoma: A Systematic Review and Practice Guideline. J Thorac Oncol. 2009;4(7):911-919.
Girard N, Ruffini E, Marx A, Faivre-Finn C, Peters S; ESMO Guidelines Committee. Thymic Epithelial Tumours: ESMO Clinical Practice Guidelines for Diagnosis, Treatment and Follow-Up. Ann Oncol. 2015;26(Suppl 5):v40-55.
Marom EM. Advances in Thymoma Imaging. J Thorac Imaging. 2013;28(2):69-80.
Last Revised: August 12, 2026
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